In recent years, laser technology has been markedly developed. In particular, small-sized solid state lasers or semiconductor lasers (hereinafter sometimes referred to as “infrared lasers”) emitting infrared rays of 760 nm to 1200 nm with a high output have become easily available. These lasers are extremely useful as a recording light source in directly making a plate based on digital data from a computer or the like. Thus, there has recently been an increasing demand for an image-recording material having a high responsiveness to such an infrared ray source, i.e., an image-recording material which undergoes a large change in solubility for a developing solution upon being irradiated with infrared rays.
As such negative-working image-recording material which can be recorded by means of an infrared laser, a recording material is described in U.S. Pat. No. 5,340,699 which comprises an infrared ray-absorbing agent, an acid generator, a resol resin and a novolak resin. However, in order to form an image, such negative-working image-recording materials require heating treatment after exposure with a laser. Therefore, there has been desired a negative-working image-recording material which does not require the heating treatment after exposure.
For example, Japanese Patent Publication No. 103171/1995 describes a recording material not requiring the heating treatment after exposure, which comprises a cyanine dye having a specific structure, an iodonium salt and an addition polymerizable compound having an ethylenically unsaturated double bond. However, this image-recording material involves a problem that discrimination between laser beam-exposed areas and laser beam-unexposed areas is obtained with difficulty by an eye after exposure and before development, that is, a problem of inferior print-out properties.